جستجوی مقالات مرتبط با کلیدواژه "third" در نشریات گروه "مکانیک"

Piezoelectric actuators and sensors have been broadly used for design of smart structures over the last two decades.
Different theoretical assumptions have been considered in order to model these structures by the researchers. In this paper, an enhanced piezolaminated sandwich beam finite element model is presented. The facing layers follow the Euler-Bernoulli assumption while the core layers are modeled with the third-order shear deformation theory (TSDT). To refine the model, the displacement-strain relationships are developed by using von Karman's nonlinear displacement-strain relation. It will be shown that this assumption generates some additional terms on the electric fields and also introduces some electromechanical potential and non-conservative work terms for the extension piezoelectric sub-layers. A variational formulation of the problem is presented. In order to develop an electromechanically coupled finite element model of the extension/shear piezolaminated beam, the electric DoFs as well as the mechanical DoFs are considered. For computing the natural frequencies, the governing equation is linearized around a static equilibrium position. Comparing natural frequencies, the effect of nonlinear terms is studied for some examples.

The problem of transient flow of incompressible third grade fluid on the two-dimensional magnetohydrodynamic (MHD) flow in a porous space is analyzed. The flow is generated due to the motion of the plate in its plane with a periodic velocity. Under the flow assumptions, the governing nonlinear partial differential equation is transformed into steady-state and transient nonlinear equations. The reduced equation for the transient flow is solved analytically using symmetry approach while the nonlinear steady-state equation is solvedusingamodifiedversionofHe’shomotopyperturbationmethod. Theeffectofseveraloperatingparameters on the flowhydromagnetic isdiscussed. The results indicated that for the considered case,t =1.5 is the moment after which the time-dependent transient motion of the fluid can be approximated with the steady-state motion, described by the steady-state solution. It is clear that, after this value of time t the time-dependent transient solution can be neglected.